package com.best.onegous.Refresh;

import com.best.onegous.R;

import android.content.Context;
import android.support.v4.widget.SwipeRefreshLayout;
import android.util.AttributeSet;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewConfiguration;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.ListView;


/**
* 继承自SwipeRefreshLayout,从而实现滑动到底部时上拉加载更多的功能.
* 
* @author mrsimple
*/
public class RefreshLayout extends SwipeRefreshLayout implements OnScrollListener {

 /**
  * 滑动到最下面时的上拉操作
  */

 private int mTouchSlop;
 /**
  * listview实例
  */
 private ListView mListView;

 /**
  * 上拉监听器, 到了最底部的上拉加载操作
  */
 private OnLoadListener mOnLoadListener;

 /**
  * ListView的加载中footer
  */
 private View mListViewFooter;

 /**
  * 按下时的y坐标
  */
 private int mYDown;
 /**
  * 抬起时的y坐标, 与mYDown一起用于滑动到底部时判断是上拉还是下拉
  */
 private int mLastY;
 /**
  * 是否在加载中 ( 上拉加载更多 )
  */
 private boolean isLoading = false;

 /**
  * @param context
  */
 public RefreshLayout(Context context) {
   this(context, null);
 }

 public RefreshLayout(Context context, AttributeSet attrs) {
   super(context, attrs);

   mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();

   mListViewFooter = LayoutInflater.from(context).inflate(R.layout.xlistview_footer, null,
       false);
 }

 @Override
 protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
   super.onLayout(changed, left, top, right, bottom);

   // 初始化ListView对象
   if (mListView == null) {
     getListView();
   }
 }

 /**
  * 获取ListView对象
  */
 private void getListView() {
   int childs = getChildCount();
   if (childs > 0) {
     View childView = getChildAt(0);
     if (childView instanceof ListView) {
       mListView = (ListView) childView;
       // 设置滚动监听器给ListView, 使得滚动的情况下也可以自动加载
       mListView.setOnScrollListener(this);
       Log.d(VIEW_LOG_TAG, "### 找到listview");
     }
   }
 }

 /*
  * (non-Javadoc)
  * @see android.view.ViewGroup#dispatchTouchEvent(android.view.MotionEvent)
  */
 @Override
 public boolean dispatchTouchEvent(MotionEvent event) {
   final int action = event.getAction();

   switch (action) {
     case MotionEvent.ACTION_DOWN:
       // 按下
       mYDown = (int) event.getRawY();
       break;

     case MotionEvent.ACTION_MOVE:
       // 移动
       mLastY = (int) event.getRawY();
       break;

     case MotionEvent.ACTION_UP:
       // 抬起
       if (canLoad()) {
         loadData();
       }
       break;
     default:
       break;
   }

   return super.dispatchTouchEvent(event);
 }

 /**
  * 是否可以加载更多, 条件是到了最底部, listview不在加载中, 且为上拉操作.
  * 
  * @return
  */
 private boolean canLoad() {
   return isBottom() && !isLoading && isPullUp();
 }

 /**
  * 判断是否到了最底部
  */
 private boolean isBottom() {

   if (mListView != null && mListView.getAdapter() != null) {
     return mListView.getLastVisiblePosition() == (mListView.getAdapter().getCount() - 1);
   }
   return false;
 }

 /**
  * 是否是上拉操作
  * 
  * @return
  */
 private boolean isPullUp() {
   return (mYDown - mLastY) >= mTouchSlop;
 }

 /**
  * 如果到了最底部,而且是上拉操作.那么执行onLoad方法
  */
 private void loadData() {
   if (mOnLoadListener != null) {
     // 设置状态
     setLoading(true);
     //
     mOnLoadListener.onLoad();
   }
 }

 /**
  * @param loading
  */
 public void setLoading(boolean loading) {
   isLoading = loading;
   if (isLoading) {
     mListView.addFooterView(mListViewFooter);
   } else {
     mListView.removeFooterView(mListViewFooter);
     mYDown = 0;
     mLastY = 0;
   }
 }

 /**
  * @param loadListener
  */
 public void setOnLoadListener(OnLoadListener loadListener) {
   mOnLoadListener = loadListener;
 }

 @Override
 public void onScrollStateChanged(AbsListView view, int scrollState) {

 }

 @Override
 public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount,
     int totalItemCount) {
   // 滚动时到了最底部也可以加载更多
   if (canLoad()) {
     loadData();
   }
 }

 /**
  * 加载更多的监听器
  * 
  * @author mrsimple
  */
 public static interface OnLoadListener {
   public void onLoad();
 }
}